The present invention relates to an arrangement for manufacturing or treating a web material. More particularly, it relates to an arrangement for manufacturing or treating a web material which has a hollow roll, two bearing pins of which one has a conduit for a heat-carrying fluid, and a displacement member arranged inside the hollow roll and extending for a greater part of the latter so as to form an annular gap between the displacement member and the roll jacket for passing the heat-carrying fluid.
In the above-described arrangement, treating of a web material, for example a synthetic plastic material, a bonded fabric or above all paper, can be performed by heating or cooling, depending upon the material. For this purpose the heat carrier is supplied through the annular gap between the displacement member and the roll jacket. By controlling the quantity or the temperature of the heat carrier, or both, the desired heat transfer condition between the web material and the outer surface of the roll can be obtained. In many cases, the roll provides not only a temperature treatment but also a mechanical treatment, such as for example a pressing treatment. Regardless of the fact that the last-mentioned treatment is performed or not, it is important that in all cases the roller has a constant diameter over its entire length. This is also true when the roll because of its great length which often lies between 5 and 10 meters is flexed and supported or compensated in another manner. When such a hollow shaft is continuously surrounded only on its smaller part by a web material to be heated or cooled, the heat tranfer between the web material and the outer surface of the roll is different in this part as compared with end parts not covered by the web material, since in the end parts heat transfer between the surrounding air and the outer surface of the roll takes place. Therefore, the temperature of the roll over its length is not constant. As a result of this, because of different thermal expansions, the roll diameter in the end region changes as compared with the central part in contact with the web material. This leads, for example in heated rolls for calendaring of paper, to the fact that the edge of the paper web is thinner than the central region, which is extremely undesirable.